main.css

body {
    margin: 0;
    padding: 0;
    color: black;
    font-family: 'Titillium Web', sans-serif;
}

h1 {
    margin-top: 0;
}

#header {
    text-align: center;
    background: rgb(97, 105, 114);
    width: 100%;
    padding-top: 5%;
    padding-bottom: 5%;
    color: white;
}

/* The switch - the box around the slider */
.switch {
    position: relative;
    display: inline-block;
    width: 90px;
    height: 34px;
}

/* Hide default HTML checkbox */
.switch input {display: none;}

/* The slider */
.slider {
    position: absolute;
    cursor: pointer;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background-color: rgb(106, 214, 106);
    -webkit-transition: .4s;
    transition: .4s;
}

.slider:before {
    position: absolute;
    content: "";
    height: 26px;
    width: 26px;
    left: 4px;
    bottom: 4px;
   background-color: white;
   -webkit-transition: .4s;
   transition: .4s;
}

/* color of slider box after click */
input:checked + .slider {
    background-color: rgb(206, 71, 71);
}

input:focus + .slider {
    box-shadow: 0 0 1px rgb(206, 71, 71);
}

input:checked + .slider:before {
    -webkit-transform: translateX(55px);
    -ms-transform: translateX(55px);
    transform: translateX(55px);
}

.slider:after
{
 content:'EASY';
 color: white;
 display: block;
 position: absolute;
 transform: translate(-50%,-50%);
 top: 50%;
 left: 65%;
 font-size: 18px;
}

input:checked + .slider:after
{  
  content:'HARD';
  left: 33%;
}

#rgbContainer {
    height: 150px;
    line-height: 150px;
    text-align: center;
    font-size: 30px;
    font-weight: bold;
 }
 
span {
     display: inline-block;
     vertical-align: middle;
     line-height: 20px;
 }

 
#choices {
    text-align: center;
}

#choicesHard {
    display: none;
}

button {
   border: none;
   outline: none;
   width: 170px;
   height: 170px;
   margin: 10px;
}

.resultAnim {
 -webkit-transition: opacity 1s;
    -moz-transition: opacity 1s;
      -o-transition: opacity 1s;
         transition: opacity 1s;
    opacity:0;
}

.dim_fast {
    opacity: 1;
}

.blinker {
-webkit-animation: boxShadow .75s linear 2;
   -moz-animation: boxShadow .75s linear 2;
    -ms-animation: boxShadow .75s linear 2;
     -o-animation: boxShadow .75s linear 2;
        animation: boxShadow .75s linear 2;
}

@-webkit-keyframes boxShadow {
    50% {
        transform: scale(1.1, 1.1);
    }
}
@-moz-keyframes boxShadow {
    50% {
        transform: scale(1.1, 1.1);
    }
}
@-o-keyframes boxShadow {
    50% {
        transform: scale(1.1, 1.1);
    }
}
@keyframes boxShadow {
    50% {
        transform: scale(1.1, 1.1);
    }
}

@media (max-width: 450px) {
    #header {
      background: rgb(54, 89, 129);
    }
    h1 {
        margin-top: 0;
        font-size: 26px;
    }
    h2 {
        font-size: 20px;
        margin: 10px;
    }
    #rgbContainer {
        text-align: center;
        font-weight: bold;
        
     }
     
    span {
        display: inline-block;
        vertical-align: middle;
        line-height: 20px;
        font-size: 20px;
     }
     
     button {
        border: none;
        outline: none;
        max-width: 90px;
        max-height: 90px;
        margin: 5px;
     }
}

#score {
    font-size: 20px;
}